Backport selected refinements from the nullability efforts

Issue: SPR-15656

spring-expression/src/main/java/org/springframework/expression/AccessException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,6 +25,14 @@ package org.springframework.expression;
 @SuppressWarnings("serial")
 public class AccessException extends Exception {
 
+	/**
+	 * Create an AccessException with a specific message.
+	 * @param message the message
+	 */
+	public AccessException(String message) {
+		super(message);
+	}
+
 	/**
 	 * Create an AccessException with a specific message and cause.
 	 * @param message the message
@@ -34,12 +42,4 @@ public class AccessException extends Exception {
 		super(message, cause);
 	}
 
-	/**
-	 * Create an AccessException with a specific message.
-	 * @param message the message
-	 */
-	public AccessException(String message) {
-		super(message);
-	}
-
 }

spring-expression/src/main/java/org/springframework/expression/ConstructorExecutor.java

@@ -36,13 +36,12 @@ public interface ConstructorExecutor {
 
 	/**
 	 * Execute a constructor in the specified context using the specified arguments.
-	 *
 	 * @param context the evaluation context in which the command is being executed
-	 * @param arguments the arguments to the constructor call, should match (in terms of
-	 *        number and type) whatever the command will need to run
+	 * @param arguments the arguments to the constructor call, should match (in terms
+	 * of number and type) whatever the command will need to run
 	 * @return the new object
 	 * @throws AccessException if there is a problem executing the command or the
-	 *         CommandExecutor is no longer valid
+	 * CommandExecutor is no longer valid
 	 */
 	TypedValue execute(EvaluationContext context, Object... arguments) throws AccessException;
 

spring-expression/src/main/java/org/springframework/expression/OperatorOverloader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,9 +17,9 @@
 package org.springframework.expression;
 
 /**
- * By default the mathematical operators {@link Operation} support simple types like
- * numbers. By providing an implementation of OperatorOverloader, a user of the expression
- * language can support these operations on other types.
+ * By default the mathematical operators {@link Operation} support simple types
+ * like numbers. By providing an implementation of OperatorOverloader, a user
+ * of the expression language can support these operations on other types.
  *
  * @author Andy Clement
  * @since 3.0
@@ -27,21 +27,21 @@ package org.springframework.expression;
 public interface OperatorOverloader {
 
 	/**
-	 * Return true if the operator overloader supports the specified operation between the
-	 * two operands and so should be invoked to handle it.
+	 * Return true if the operator overloader supports the specified operation
+	 * between the two operands and so should be invoked to handle it.
 	 * @param operation the operation to be performed
 	 * @param leftOperand the left operand
 	 * @param rightOperand the right operand
-	 * @return true if the OperatorOverloader supports the specified operation between the
-	 *         two operands
+	 * @return true if the OperatorOverloader supports the specified operation
+	 * between the two operands
 	 * @throws EvaluationException if there is a problem performing the operation
 	 */
 	boolean overridesOperation(Operation operation, Object leftOperand, Object rightOperand)
 			throws EvaluationException;
 
 	/**
-	 * Execute the specified operation on two operands, returning a result. See
-	 * {@link Operation} for supported operations.
+	 * Execute the specified operation on two operands, returning a result.
+	 * See {@link Operation} for supported operations.
 	 * @param operation the operation to be performed
 	 * @param leftOperand the left operand
 	 * @param rightOperand the right operand

spring-expression/src/main/java/org/springframework/expression/common/TemplateAwareExpressionParser.java

@@ -112,6 +112,7 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 		String prefix = context.getExpressionPrefix();
 		String suffix = context.getExpressionSuffix();
 		int startIdx = 0;
+
 		while (startIdx < expressionString.length()) {
 			int prefixIndex = expressionString.indexOf(prefix, startIdx);
 			if (prefixIndex >= startIdx) {
@@ -126,22 +127,18 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 							"No ending suffix '" + suffix + "' for expression starting at character " +
 							prefixIndex + ": " + expressionString.substring(prefixIndex));
 				}
-
 				if (suffixIndex == afterPrefixIndex) {
 					throw new ParseException(expressionString, prefixIndex,
 							"No expression defined within delimiter '" + prefix + suffix +
 							"' at character " + prefixIndex);
 				}
-
 				String expr = expressionString.substring(prefixIndex + prefix.length(), suffixIndex);
 				expr = expr.trim();
-
 				if (expr.isEmpty()) {
 					throw new ParseException(expressionString, prefixIndex,
 							"No expression defined within delimiter '" + prefix + suffix +
 							"' at character " + prefixIndex);
 				}
-
 				expressions.add(doParseExpression(expr, context));
 				startIdx = suffixIndex + suffix.length();
 			}
@@ -151,6 +148,7 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 				startIdx = expressionString.length();
 			}
 		}
+
 		return expressions.toArray(new Expression[expressions.size()]);
 	}
 

spring-expression/src/main/java/org/springframework/expression/spel/ExpressionState.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,6 +32,7 @@ import org.springframework.expression.TypeComparator;
 import org.springframework.expression.TypeConverter;
 import org.springframework.expression.TypedValue;
 import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
 
 /**
  * An ExpressionState is for maintaining per-expression-evaluation state, any changes to
@@ -53,6 +54,12 @@ public class ExpressionState {
 
 	private final TypedValue rootObject;
 
+	private final SpelParserConfiguration configuration;
+
+	private Stack<TypedValue> contextObjects;
+
+	private Stack<VariableScope> variableScopes;
+
 	// When entering a new scope there is a new base object which should be used
 	// for '#this' references (or to act as a target for unqualified references).
 	// This stack captures those objects at each nested scope level.
@@ -62,12 +69,6 @@ public class ExpressionState {
 	// element from list1
 	private Stack<TypedValue> scopeRootObjects;
 
-	private final SpelParserConfiguration configuration;
-
-	private Stack<VariableScope> variableScopes;
-
-	private Stack<TypedValue> contextObjects;
-
 
 	public ExpressionState(EvaluationContext context) {
 		this(context, context.getRootObject(), new SpelParserConfiguration(false, false));
@@ -105,7 +106,7 @@ public class ExpressionState {
 	 * The active context object is what unqualified references to properties/etc are resolved against.
 	 */
 	public TypedValue getActiveContextObject() {
-		if (this.contextObjects == null || this.contextObjects.isEmpty()) {
+		if (CollectionUtils.isEmpty(this.contextObjects)) {
 			return this.rootObject;
 		}
 		return this.contextObjects.peek();
@@ -130,7 +131,7 @@ public class ExpressionState {
 	}
 
 	public TypedValue getScopeRootContextObject() {
-		if (this.scopeRootObjects == null || this.scopeRootObjects.isEmpty()) {
+		if (CollectionUtils.isEmpty(this.scopeRootObjects)) {
 			return this.rootObject;
 		}
 		return this.scopeRootObjects.peek();
@@ -142,12 +143,7 @@ public class ExpressionState {
 
 	public TypedValue lookupVariable(String name) {
 		Object value = this.relatedContext.lookupVariable(name);
-		if (value == null) {
-			return TypedValue.NULL;
-		}
-		else {
-			return new TypedValue(value);
-		}
+		return (value != null ? new TypedValue(value) : TypedValue.NULL);
 	}
 
 	public TypeComparator getTypeComparator() {

spring-expression/src/main/java/org/springframework/expression/spel/SpelParserConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,7 +18,6 @@ package org.springframework.expression.spel;
 
 import org.springframework.core.SpringProperties;
 
-
 /**
  * Configuration object for the SpEL expression parser.
  *
@@ -106,35 +105,35 @@ public class SpelParserConfiguration {
 
 
 	/**
-	 * @return the configuration mode for parsers using this configuration object
+	 * Return the configuration mode for parsers using this configuration object.
 	 */
 	public SpelCompilerMode getCompilerMode() {
 		return this.compilerMode;
 	}
 
 	/**
-	 * @return the ClassLoader to use as the basis for expression compilation
+	 * Return the ClassLoader to use as the basis for expression compilation.
 	 */
 	public ClassLoader getCompilerClassLoader() {
 		return this.compilerClassLoader;
 	}
 
 	/**
-	 * @return {@code true} if {@code null} references should be automatically grown
+	 * Return {@code true} if {@code null} references should be automatically grown.
 	 */
 	public boolean isAutoGrowNullReferences() {
 		return this.autoGrowNullReferences;
 	}
 
 	/**
-	 * @return {@code true} if collections should be automatically grown
+	 * Return {@code true} if collections should be automatically grown.
 	 */
 	public boolean isAutoGrowCollections() {
 		return this.autoGrowCollections;
 	}
 
 	/**
-	 * @return the maximum size that a collection can auto grow
+	 * Return the maximum size that a collection can auto grow.
 	 */
 	public int getMaximumAutoGrowSize() {
 		return this.maximumAutoGrowSize;

spring-expression/src/main/java/org/springframework/expression/spel/ast/BeanReference.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,7 +37,7 @@ public class BeanReference extends SpelNodeImpl {
 	private final String beanName;
 
 
-	public BeanReference(int pos,String beanName) {
+	public BeanReference(int pos, String beanName) {
 		super(pos);
 		this.beanName = beanName;
 	}

spring-expression/src/main/java/org/springframework/expression/spel/ast/CompoundExpression.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,7 +31,7 @@ import org.springframework.expression.spel.SpelEvaluationException;
  */
 public class CompoundExpression extends SpelNodeImpl {
 
-	public CompoundExpression(int pos,SpelNodeImpl... expressionComponents) {
+	public CompoundExpression(int pos, SpelNodeImpl... expressionComponents) {
 		super(pos, expressionComponents);
 		if (expressionComponents.length < 2) {
 			throw new IllegalStateException("Do not build compound expressions with less than two entries: " +

spring-expression/src/main/java/org/springframework/expression/spel/ast/FunctionReference.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -59,7 +59,7 @@ public class FunctionReference extends SpelNodeImpl {
 
 
 	public FunctionReference(String functionName, int pos, SpelNodeImpl... arguments) {
-		super(pos,arguments);
+		super(pos, arguments);
 		this.name = functionName;
 	}
 
@@ -107,15 +107,15 @@ public class FunctionReference extends SpelNodeImpl {
 					SpelMessage.FUNCTION_MUST_BE_STATIC, ClassUtils.getQualifiedMethodName(method), this.name);
 		}
 
-		argumentConversionOccurred = false;
+		this.argumentConversionOccurred = false;
 		// Convert arguments if necessary and remap them for varargs if required
 		if (functionArgs != null) {
 			TypeConverter converter = state.getEvaluationContext().getTypeConverter();
-			argumentConversionOccurred = ReflectionHelper.convertAllArguments(converter, functionArgs, method);
+			this.argumentConversionOccurred = ReflectionHelper.convertAllArguments(converter, functionArgs, method);
 		}
 		if (method.isVarArgs()) {
-			functionArgs =
-					ReflectionHelper.setupArgumentsForVarargsInvocation(method.getParameterTypes(), functionArgs);
+			functionArgs = ReflectionHelper.setupArgumentsForVarargsInvocation(
+					method.getParameterTypes(), functionArgs);
 		}
 
 		try {

spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -51,7 +51,7 @@ import org.springframework.expression.spel.support.ReflectivePropertyAccessor;
 // TODO support correct syntax for multidimensional [][][] and not [,,,]
 public class Indexer extends SpelNodeImpl {
 
-	private static enum IndexedType {ARRAY, LIST, MAP, STRING, OBJECT}
+	private enum IndexedType {ARRAY, LIST, MAP, STRING, OBJECT}
 
 
 	// These fields are used when the indexer is being used as a property read accessor.

spring-expression/src/main/java/org/springframework/expression/spel/ast/NullLiteral.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,7 +29,7 @@ import org.springframework.expression.spel.CodeFlow;
 public class NullLiteral extends Literal {
 
 	public NullLiteral(int pos) {
-		super(null,pos);
+		super(null, pos);
 		this.exitTypeDescriptor = "Ljava/lang/Object";
 	}
 

spring-expression/src/main/java/org/springframework/expression/spel/ast/OpAnd.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,7 +44,7 @@ public class OpAnd extends Operator {
 
 	@Override
 	public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
-		if (getBooleanValue(state, getLeftOperand()) == false) {
+		if (!getBooleanValue(state, getLeftOperand())) {
 			// no need to evaluate right operand
 			return BooleanTypedValue.FALSE;
 		}

spring-expression/src/main/java/org/springframework/expression/spel/ast/OpPlus.java

@@ -192,8 +192,8 @@ public class OpPlus extends Operator {
 	private void walk(MethodVisitor mv, CodeFlow cf, SpelNodeImpl operand) {
 		if (operand instanceof OpPlus) {
 			OpPlus plus = (OpPlus)operand;
-			walk(mv,cf,plus.getLeftOperand());
-			walk(mv,cf,plus.getRightOperand());
+			walk(mv, cf, plus.getLeftOperand());
+			walk(mv, cf, plus.getRightOperand());
 		}
 		else {
 			cf.enterCompilationScope();

spring-expression/src/main/java/org/springframework/expression/spel/ast/Operator.java

@@ -87,7 +87,7 @@ public abstract class Operator extends SpelNodeImpl {
 
 	protected boolean isCompilableOperatorUsingNumerics() {
 		SpelNodeImpl left = getLeftOperand();
-		SpelNodeImpl right= getRightOperand();
+		SpelNodeImpl right = getRightOperand();
 		if (!left.isCompilable() || !right.isCompilable()) {
 			return false;
 		}
@@ -273,11 +273,11 @@ public abstract class Operator extends SpelNodeImpl {
 			boolean rightNumeric = CodeFlow.isPrimitiveOrUnboxableSupportedNumberOrBoolean(rd);
 			
 			// If the declared descriptors aren't providing the information, try the actual descriptors
-			if (!leftNumeric && !ld.equals(leftActualDescriptor)) {
+			if (!leftNumeric && !ObjectUtils.nullSafeEquals(ld, leftActualDescriptor)) {
 				ld = leftActualDescriptor;
 				leftNumeric = CodeFlow.isPrimitiveOrUnboxableSupportedNumberOrBoolean(ld);
 			}
-			if (!rightNumeric && !rd.equals(rightActualDescriptor)) {
+			if (!rightNumeric && !ObjectUtils.nullSafeEquals(rd, rightActualDescriptor)) {
 				rd = rightActualDescriptor;
 				rightNumeric = CodeFlow.isPrimitiveOrUnboxableSupportedNumberOrBoolean(rd);
 			}

spring-expression/src/main/java/org/springframework/expression/spel/ast/OperatorMatches.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

spring-expression/src/main/java/org/springframework/expression/spel/ast/SpelNodeImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -77,6 +77,7 @@ public abstract class SpelNodeImpl implements SpelNode, Opcodes {
 	}
 
 
+	@Deprecated
 	protected SpelNodeImpl getPreviousChild() {
 		SpelNodeImpl result = null;
 		if (this.parent != null) {
@@ -214,9 +215,9 @@ public abstract class SpelNodeImpl implements SpelNode, Opcodes {
 
 	
 	/**
-	 * Generate code that handles building the argument values for the specified method. This method will take account
-	 * of whether the invoked method is a varargs method and if it is then the argument values will be appropriately
-	 * packaged into an array.
+	 * Generate code that handles building the argument values for the specified method.
+	 * This method will take account of whether the invoked method is a varargs method
+	 * and if it is then the argument values will be appropriately packaged into an array.
 	 * @param mv the method visitor where code should be generated
 	 * @param cf the current codeflow
 	 * @param member the method or constructor for which arguments are being setup
@@ -226,7 +227,7 @@ public abstract class SpelNodeImpl implements SpelNode, Opcodes {
 		String[] paramDescriptors = null;
 		boolean isVarargs = false;
 		if (member instanceof Constructor) {
-			Constructor<?> ctor = (Constructor<?>)member;
+			Constructor<?> ctor = (Constructor<?>) member;
 			paramDescriptors = CodeFlow.toDescriptors(ctor.getParameterTypes());
 			isVarargs = ctor.isVarArgs();
 		}
@@ -246,25 +247,25 @@ public abstract class SpelNodeImpl implements SpelNode, Opcodes {
 				generateCodeForArgument(mv, cf, arguments[p], paramDescriptors[p]);
 			}
 			
-			SpelNodeImpl lastchild = (childCount == 0 ? null : arguments[childCount - 1]);
-			String arraytype = paramDescriptors[paramDescriptors.length - 1];
+			SpelNodeImpl lastChild = (childCount == 0 ? null : arguments[childCount - 1]);
+			String arrayType = paramDescriptors[paramDescriptors.length - 1];
 			// Determine if the final passed argument is already suitably packaged in array
 			// form to be passed to the method
-			if (lastchild != null && lastchild.getExitDescriptor().equals(arraytype)) {
-				generateCodeForArgument(mv, cf, lastchild, paramDescriptors[p]);
+			if (lastChild != null && arrayType.equals(lastChild.getExitDescriptor())) {
+				generateCodeForArgument(mv, cf, lastChild, paramDescriptors[p]);
 			}
 			else {
-				arraytype = arraytype.substring(1); // trim the leading '[', may leave other '['		
+				arrayType = arrayType.substring(1); // trim the leading '[', may leave other '['
 				// build array big enough to hold remaining arguments
-				CodeFlow.insertNewArrayCode(mv, childCount - p, arraytype);
+				CodeFlow.insertNewArrayCode(mv, childCount - p, arrayType);
 				// Package up the remaining arguments into the array
 				int arrayindex = 0;
 				while (p < childCount) {
 					SpelNodeImpl child = arguments[p];
 					mv.visitInsn(DUP);
 					CodeFlow.insertOptimalLoad(mv, arrayindex++);
-					generateCodeForArgument(mv, cf, child, arraytype);
-					CodeFlow.insertArrayStore(mv, arraytype);
+					generateCodeForArgument(mv, cf, child, arrayType);
+					CodeFlow.insertArrayStore(mv, arrayType);
 					p++;
 				}
 			}
@@ -283,15 +284,16 @@ public abstract class SpelNodeImpl implements SpelNode, Opcodes {
 	protected static void generateCodeForArgument(MethodVisitor mv, CodeFlow cf, SpelNodeImpl argument, String paramDesc) {
 		cf.enterCompilationScope();
 		argument.generateCode(mv, cf);
-		boolean primitiveOnStack = CodeFlow.isPrimitive(cf.lastDescriptor());
+		String lastDesc = cf.lastDescriptor();
+		boolean primitiveOnStack = CodeFlow.isPrimitive(lastDesc);
 		// Check if need to box it for the method reference?
 		if (primitiveOnStack && paramDesc.charAt(0) == 'L') {
-			CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
+			CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
 		}
 		else if (paramDesc.length() == 1 && !primitiveOnStack) {
-			CodeFlow.insertUnboxInsns(mv, paramDesc.charAt(0), cf.lastDescriptor());
+			CodeFlow.insertUnboxInsns(mv, paramDesc.charAt(0), lastDesc);
 		}
-		else if (!cf.lastDescriptor().equals(paramDesc)) {
+		else if (!paramDesc.equals(lastDesc)) {
 			// This would be unnecessary in the case of subtyping (e.g. method takes Number but Integer passed in)
 			CodeFlow.insertCheckCast(mv, paramDesc);
 		}

spring-expression/src/main/java/org/springframework/expression/spel/standard/SpelCompiler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -88,14 +88,13 @@ public class SpelCompiler implements Opcodes {
 
 
 	/**
-	 * Attempt compilation of the supplied expression. A check is
-	 * made to see if it is compilable before compilation proceeds. The
-	 * check involves visiting all the nodes in the expression Ast and
-	 * ensuring enough state is known about them that bytecode can
-	 * be generated for them.
+	 * Attempt compilation of the supplied expression. A check is made to see
+	 * if it is compilable before compilation proceeds. The check involves
+	 * visiting all the nodes in the expression Ast and ensuring enough state
+	 * is known about them that bytecode can be generated for them.
 	 * @param expression the expression to compile
-	 * @return an instance of the class implementing the compiled expression, or null
-	 * if compilation is not possible
+	 * @return an instance of the class implementing the compiled expression,
+	 * or {@code null} if compilation is not possible
 	 */
 	public CompiledExpression compile(SpelNodeImpl expression) {
 		if (expression.isCompilable()) {

spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectionHelper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,6 +27,7 @@ import org.springframework.expression.TypeConverter;
 import org.springframework.expression.spel.SpelEvaluationException;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.CollectionUtils;
 import org.springframework.util.MethodInvoker;
 
 /**
@@ -141,8 +142,8 @@ public class ReflectionHelper {
 	static ArgumentsMatchInfo compareArgumentsVarargs(
 			List<TypeDescriptor> expectedArgTypes, List<TypeDescriptor> suppliedArgTypes, TypeConverter typeConverter) {
 
-		Assert.isTrue(expectedArgTypes != null && expectedArgTypes.size() > 0,
-				"Expected arguments must at least include one array (the vargargs parameter)");
+		Assert.isTrue(!CollectionUtils.isEmpty(expectedArgTypes),
+				"Expected arguments must at least include one array (the varargs parameter)");
 		Assert.isTrue(expectedArgTypes.get(expectedArgTypes.size() - 1).isArray(),
 				"Final expected argument should be array type (the varargs parameter)");
 

spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectiveMethodExecutor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,6 +44,7 @@ public class ReflectiveMethodExecutor implements MethodExecutor {
 
 	private boolean argumentConversionOccurred = false;
 
+
 	public ReflectiveMethodExecutor(Method method) {
 		this.method = method;
 		if (method.isVarArgs()) {
@@ -55,6 +56,7 @@ public class ReflectiveMethodExecutor implements MethodExecutor {
 		}
 	}
 
+
 	public Method getMethod() {
 		return this.method;
 	}
@@ -68,8 +70,8 @@ public class ReflectiveMethodExecutor implements MethodExecutor {
 	 * method (if there is one!). For toString() it may walk as far as Object.
 	 */
 	public Class<?> getPublicDeclaringClass() {
-		if (!computedPublicDeclaringClass) {
-			this.publicDeclaringClass = discoverPublicClass(method, method.getDeclaringClass());
+		if (!this.computedPublicDeclaringClass) {
+			this.publicDeclaringClass = discoverPublicClass(this.method, this.method.getDeclaringClass());
 			this.computedPublicDeclaringClass = true;
 		}
 		return this.publicDeclaringClass;

spring-expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -93,14 +93,23 @@ public class StandardEvaluationContext implements EvaluationContext {
 		return this.rootObject;
 	}
 
-	public void addConstructorResolver(ConstructorResolver resolver) {
-		ensureConstructorResolversInitialized();
-		this.constructorResolvers.add(this.constructorResolvers.size() - 1, resolver);
+	public void setPropertyAccessors(List<PropertyAccessor> propertyAccessors) {
+		this.propertyAccessors = propertyAccessors;
 	}
 
-	public boolean removeConstructorResolver(ConstructorResolver resolver) {
-		ensureConstructorResolversInitialized();
-		return this.constructorResolvers.remove(resolver);
+	@Override
+	public List<PropertyAccessor> getPropertyAccessors() {
+		ensurePropertyAccessorsInitialized();
+		return this.propertyAccessors;
+	}
+
+	public void addPropertyAccessor(PropertyAccessor accessor) {
+		ensurePropertyAccessorsInitialized();
+		this.propertyAccessors.add(this.propertyAccessors.size() - 1, accessor);
+	}
+
+	public boolean removePropertyAccessor(PropertyAccessor accessor) {
+		return this.propertyAccessors.remove(accessor);
 	}
 
 	public void setConstructorResolvers(List<ConstructorResolver> constructorResolvers) {
@@ -113,14 +122,14 @@ public class StandardEvaluationContext implements EvaluationContext {
 		return this.constructorResolvers;
 	}
 
-	public void addMethodResolver(MethodResolver resolver) {
-		ensureMethodResolversInitialized();
-		this.methodResolvers.add(this.methodResolvers.size() - 1, resolver);
+	public void addConstructorResolver(ConstructorResolver resolver) {
+		ensureConstructorResolversInitialized();
+		this.constructorResolvers.add(this.constructorResolvers.size() - 1, resolver);
 	}
 
-	public boolean removeMethodResolver(MethodResolver methodResolver) {
-		ensureMethodResolversInitialized();
-		return this.methodResolvers.remove(methodResolver);
+	public boolean removeConstructorResolver(ConstructorResolver resolver) {
+		ensureConstructorResolversInitialized();
+		return this.constructorResolvers.remove(resolver);
 	}
 
 	public void setMethodResolvers(List<MethodResolver> methodResolvers) {
@@ -133,6 +142,16 @@ public class StandardEvaluationContext implements EvaluationContext {
 		return this.methodResolvers;
 	}
 
+	public void addMethodResolver(MethodResolver resolver) {
+		ensureMethodResolversInitialized();
+		this.methodResolvers.add(this.methodResolvers.size() - 1, resolver);
+	}
+
+	public boolean removeMethodResolver(MethodResolver methodResolver) {
+		ensureMethodResolversInitialized();
+		return this.methodResolvers.remove(methodResolver);
+	}
+
 	public void setBeanResolver(BeanResolver beanResolver) {
 		this.beanResolver = beanResolver;
 	}
@@ -142,25 +161,6 @@ public class StandardEvaluationContext implements EvaluationContext {
 		return this.beanResolver;
 	}
 
-	public void addPropertyAccessor(PropertyAccessor accessor) {
-		ensurePropertyAccessorsInitialized();
-		this.propertyAccessors.add(this.propertyAccessors.size() - 1, accessor);
-	}
-
-	public boolean removePropertyAccessor(PropertyAccessor accessor) {
-		return this.propertyAccessors.remove(accessor);
-	}
-
-	public void setPropertyAccessors(List<PropertyAccessor> propertyAccessors) {
-		this.propertyAccessors = propertyAccessors;
-	}
-
-	@Override
-	public List<PropertyAccessor> getPropertyAccessors() {
-		ensurePropertyAccessorsInitialized();
-		return this.propertyAccessors;
-	}
-
 	public void setTypeLocator(TypeLocator typeLocator) {
 		Assert.notNull(typeLocator, "TypeLocator must not be null");
 		this.typeLocator = typeLocator;
@@ -169,7 +169,7 @@ public class StandardEvaluationContext implements EvaluationContext {
 	@Override
 	public TypeLocator getTypeLocator() {
 		if (this.typeLocator == null) {
-			 this.typeLocator = new StandardTypeLocator();
+			this.typeLocator = new StandardTypeLocator();
 		}
 		return this.typeLocator;
 	}
@@ -244,6 +244,7 @@ public class StandardEvaluationContext implements EvaluationContext {
 		}
 	}
 
+
 	private void ensurePropertyAccessorsInitialized() {
 		if (this.propertyAccessors == null) {
 			initializePropertyAccessors();
@@ -258,6 +259,20 @@ public class StandardEvaluationContext implements EvaluationContext {
 		}
 	}
 
+	private void ensureConstructorResolversInitialized() {
+		if (this.constructorResolvers == null) {
+			initializeConstructorResolvers();
+		}
+	}
+
+	private synchronized void initializeConstructorResolvers() {
+		if (this.constructorResolvers == null) {
+			List<ConstructorResolver> defaultResolvers = new ArrayList<ConstructorResolver>();
+			defaultResolvers.add(new ReflectiveConstructorResolver());
+			this.constructorResolvers = defaultResolvers;
+		}
+	}
+
 	private void ensureMethodResolversInitialized() {
 		if (this.methodResolvers == null) {
 			initializeMethodResolvers();
@@ -273,18 +288,4 @@ public class StandardEvaluationContext implements EvaluationContext {
 		}
 	}
 
-	private void ensureConstructorResolversInitialized() {
-		if (this.constructorResolvers == null) {
-			initializeConstructorResolvers();
-		}
-	}
-
-	private synchronized void initializeConstructorResolvers() {
-		if (this.constructorResolvers == null) {
-			List<ConstructorResolver> defaultResolvers = new ArrayList<ConstructorResolver>();
-			defaultResolvers.add(new ReflectiveConstructorResolver());
-			this.constructorResolvers = defaultResolvers;
-		}
-	}
-
 }

spring-expression/src/main/java/org/springframework/expression/spel/support/StandardTypeConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -67,8 +67,9 @@ public class StandardTypeConverter implements TypeConverter {
 			return this.conversionService.convert(value, sourceType, targetType);
 		}
 		catch (ConversionException ex) {
-			throw new SpelEvaluationException(
-					ex, SpelMessage.TYPE_CONVERSION_ERROR, sourceType.toString(), targetType.toString());
+			throw new SpelEvaluationException(ex, SpelMessage.TYPE_CONVERSION_ERROR,
+					(sourceType != null ? sourceType.toString() : (value != null ? value.getClass().getName() : "null")),
+					targetType.toString());
 		}
 	}